1. Technical Field
Several aspects of the present invention relate to a manufacturing method of an electrode assembly, an electrode assembly, and a battery.
2. Related Art
A lithium battery using lithium or a lithium-containing material for a negative electrode has a light weight and large capacity, and a high voltage can be obtained by suitably combining with a positive electrode. Accordingly, the lithium battery is widely used as a battery for a mobile electronic apparatus, a camera, a clock, an electric tool, and a hybrid automobile. However, generally, lithium has high activity and an organic electrolytic solution is used in the lithium battery, and accordingly, ignition or explosion may occur on the occurrence of a short circuit. Therefore, it is important to ensure safety in the design of the lithium battery.
As one of methods for improving the safety, the electrolytic solution may not be used (de-electrolytic solution). As an example of the de-electrolytic solution, a lithium polymer battery using a gel polymer electrolyte has been developed. However, since the gel polymer electrolyte is obtained by impregnating polymer gel with an organic electrolyte, the problem of the ignition or the explosion still remains.
As another example of the de-electrolytic solution, a lithium battery using a ceramic electrolyte (inorganic solid electrolyte) has been developed (for example, see JP-A-2006-277997, JP-A-2004-179158, and Japanese Patent No. 4615339). When the ceramic electrolyte is used, ions moving in the electrolyte due to a cell reaction are only lithium ions, and accordingly, a side reaction substantially does not occur. In addition, since a combustible organic solution is not used, it is not necessary to use a sealing member or a liquid sealing structure, and thus it is possible to further realize miniaturization and thin thickness.
In the technology disclosed in JP-A-2006-277997, contact in a boundary of ceramic electrolyte powder and an electrode active material or a boundary of the ceramic electrolyte powder and the ceramic electrolyte powder may not be sufficient, and excellent battery output may not be obtained. In addition, the boundary contact may be unstable due to a change in volume accompanied with a charge-discharge cycle, and therefore, a cycle life may be shortened.
In the technology disclosed in JP-A-2004-179158, it is difficult to manufacture a battery having sufficient capacity. In order to obtain the sufficient capacity for a battery, it is necessary to manufacture a battery having a total thickness of an active material exceeding 100 μm, but it is difficult to manufacture a battery having the thickness thereof exceeding 100 μm, in the technology disclosed in JP-A-2004-179158.
In the technology disclosed in Japanese Patent No. 4615339, solid phase diffusion of Li0.35La0.55TiO3 which is a solid electrolyte and LiCoO2 which is a battery active material is performed in a manufacturing step, and electrical characteristics may decrease.